Threading rail means for strip stock feeding apparatus



July 18, 1967 B. E. BARINGER ETAL THREADING RAIL MEANS FOR STRIP STOCK FEEDING APPARATUS Filed April 22, 1964 6 Sheets-Sheet l FIG-5 INVENTOR. MARVIN A- HOLE JOHN A- BERLYN E.BAKINGER paw M*W ATTORNEYS y 1967 B. E. BARINGER ETAL 3,

THREADING RAIL MEANS FOR STRIP STOCK FEEDING APPARATUS 6 Sheets-Sheet 2' Filed April 22, 1964 FIG. 3-

R E m RE. I RR mmEA m fi W m m m m v R mm AOE M B w W B FIG.2.-

July 18, 1967 B. E. BARlNGER ETAL 3,

THREADING RAIL MEANS FOR STRIP STOCK FEEDING APPARATUS Filed April 22, 1964 6 Sheets-Sheet 5 FIG- 4.

INVENTOR. MARVIN A. HOLE JOHN A. HUBER BY BERLYN EJARWGER ATTORNEYS 'IIIII'IIIIII y 1957 a. E. BARINGER ETAL 3,

THREADING RAIL MEANS FOR STRIP STOCK FEEDING APPARATUS 6 Sheets-Sheet 4 Filed April 22, 1964 m f 1 w H .H @in m h .wimuwziwwm 3% @Q Q9 3 $8 H om B Q i mu w i Q Q mm July 18, 19 7 B. E. BARINGER ETAL 3,331,542

THREADING RAIL MEANS FOR STRIP STOCK FEEDING APPARATUS 6 Sheets-Sheet 5 Filed April 22, 1964 N mm E R6 EN. 0 I m wm m -H m .5 Mr N NAN V L r R R T E A Mm y 13, 1957 B. E. BARINGER ETAL 3,

THREADING RAIL MEANS FOR STRIP STOCK FEEDING APPARATUS Filed April 22, 1964 6 Sheets-Sheet 6 mlllwm IN VENTOR.

R E m E R mam M w Jr W A E R m N m W .m E J m M! United States Patent THREADING RAIL MEANS FOR STRIP STOCK FEEDING APPARATUS Berlyn E. Baringer and Marvin A. Hole, Livonia, and

John A. Huber, Birmingham, Mich., assignors to Coilfeed Systems, Inc., Detroit, Mich., a corporation of Michigan Filed Apr. 22, 1964, Ser. No. 361,823 Claims. (Cl. 226-91) This invention relates generally to the strip stock feeding art, and more particularly to a novel and improved strip stock support roll and threading rail apparatus.

Heretofore the threading rails employed in strip stock processing machines have been movable toward and away from each other by means of a pair of left and right hand thread screws. A disadvantage of the screw driven threading rail structures is that there is a large power loss encountered in the operating of such devices. The screws are long and there is a tendency for them to sag and such sagging increases operating friction which results in a power loss and low efiiciency in such devices. Another prior art type threading rail apparatus is that known as the drawbridge type wherein the rails pivot into position. A disadvantage of the drawbridge type of threading rail is that heavy stock tends to make these rails sag because of their inherent construction.

In view of the foregoing, it is an important object of the present invention to provide a novel and improved threading rail and support roll apparatus which is adapted to overcome the aforementioned disadvantages.

It is another object of the present invention to provide a novel and improved threading rail apparatus for use in strip stock processing machines which is adapted to be operated by an economical and fast operating power means, and wherein the threading rails are moved laterally inwardly and outwardly by means of a novel drive chain and fluid cylinder arrangement.

It is still another object of the present invention to provide a novel and improved support roll and threading rail apparatus for use in a strip stock processing machine which is simple and compact in construction, economical of manufacture and efficient in operation.

It is still another object of the present invention to provide a novel and improved strip stock threading rail apparatus which may be quickly and easily adjusted to feed strip stock into a processing machine in an off center position.

It is still a further object of the present invention to provide a novel and improved support roll and threading rail apparatus for a strip stock processing machine which incorporates a novel support roll for absorbing shock in the strip stock as it is fed into a processing machine.

Other objects, features and advantages of this invention will be apparent from the following detailed description, appended claims, and accompanying drawings.

In the drawings:

FIG. 1 is an elevational view of a first threading rail embodiment made in accordance with the principles of the present invention;

FIG. 2 is a fragmentary, broken, elevational sectional view of the structure illustrated in FIG. 1, taken along the line 22 thereof, and looking in the direction of the arrows;

FIG. 3 is a fragmentary, enlarged, broken, elevational sectional View of the structure illustrated in FIG. 1, taken along the line 3-3 thereof, and looking in the direction of the arrows;

FIG. 4 is a fragmentary, enlarged, broken, horizontal sectional view of the structure illustrated in FIG. 1, taken along the line 44 thereof and looking in the direction of the arrows;

FIG. 5 is a fragmentary, elevational view of the feeding machine end of a second threading rail embodiment made in accordance with the principles of the present invention;

FIGS. 6 and 6A are enlarged, broken, sectional views of the structure illustrated in FIG. 5, taken along the line 6-6 thereof and looking in the direction of the arrows;

FIG. 7 is a fragmentary, broken, sectional view of a brake apparatus employed with the second embodiment of the invention illustrated in FIGS. 5 and 6; and,

FIG. 8 is a side elevational view of the brake structure illustrated in FIG. 7, taken along the line 8-8 thereof and looking in the direction of the arrows.

Referring now to the drawings and in particular to FIG. 1, the numeral 10 generally designates a threading rail and support roll apparatus adapted to feed strip stock material from a strip stock straightener machine, generally indicated by the numeral 11, to a feeding machine generally indicated by the numeral 12. The strip stock is fed to the stock straightener machine from a supply coil of the stock in the usual manner. The numeral 13 designates the strip stock which is being fed from the straightening machine 11 to the feeding machine 12. As the strip stock 13 leaves the straightening machine 11, it loops down below the floor level and then up and into the stock-length feeding machine 12. The stock-length feeding machine 12 feeds the strip stock to a press, a shear, or other type of strip material working apparatus. The pit and the entire loop of the strip stock and the means to control the loop have not been shown since they do not form any part of this invention. It will be understood that the straightener machine 11 and the strip stock feeding machine 12 are merely illustrative of the type processing machines with which the present invention may be used.

As shown in FIGS. 1 and 3, the strip stock 13 is guided downwardly from the straightening machine 11 by a first support roll assembly comprising a plurality of pairs of aligned support rolls as 14 and 15. The support roll assembly includes the pair of vertical spaced apart frame plate members 16 and 17 which are adapted to be fixedly connected to the housing of the straightening assembly 11 by any suitable means, as by welding. The support roll frame assembly further includes the intermediate vertical frame plate 18 which is also fixedly secured to the straightening machine 11. As shown in FIG. 3, a horizontally disposed support shaft 19 is carried by the frame plates 16, 17 and 18 and is secured in place in suitable holes formed through these plates by any suitable means. The support roll 14 is rotatably mounted on the support shaft 19 by means of the bearings 20 and 21, and it is held in place against axial movement on the shaft 19 by any suitable means, as by the retainer collars 22 and 23. The support roll 15 is similarly rotatably mounted on the other end of the support shaft 19 between the frame plates 16 and 18 by means of the bearing members 24 and 25 and the retainer collars 26 and 27. As shown in FIG. 1, the upper edges of the support roll frame plates 16, 17 and 18 curve forwardly and downwardly in accordance with the shape of the loop which is formed by the strip stock 13. A plurality of additional rollers 14 and 15 are mounted along the upper edge of the frame plates 16, 17 and 18 in spaced apart positions, and these additional support rolls are marked with the corresponding reference numerals as given to the rolls 14 and 15, followed by the small letters a, b and 0. These additional support rolls are operatively mounted on the support shafts 19a, 1% and 190. The support rolls 14 and 15 may be made from any suitable material, as for example, from a suitable metal.

As shown in FIG. 4, the ends of the support roll frame plates 16, 17 and 18 are interconnected by means of the tie rods 28 and 31. The tie rod 28 fixedly interconnects the plates 17 and 18 and is held in place by means of the lock nuts 29 and 30. The tie rod 31 fixedly interconnects the frame plates 16 and 18 and is fixed in place by means of the lock nuts 32 and 33.

As shown in FIGS. 1 and 4, the strip material 13 is fed into the stock-length feeding machine 12 by means of a second support roll assembly which is constructed substantially similar to the aforedescribed first support roll assembly, but which is reversed in position therefrom. Accordingly, in FIGS. 1 and 4, the same reference numerals have been applied to the support roll assembly which guides the strip stock material 13 into the machine 12. As shown in FIG. 4, the second support roll assembly is slightly modified in that the lower support rolls 14d and 15d are provided with a rubber covering as 34 and 35 so as to cushion the shock of the deceleration and acceleration of the strip stock material as it is fed into the machine 12.

As shown in FIG. 4, the threading rail assembly includes the longitudinally extended, spaced apart rails 36 and 37 which are operatively mounted between the aforedescribed first and second support roll assemblies by the following described structure. As shown in FIG. 4, the threading rail 36 .is horizontally disposed and is provided on the ends thereof with the downwardly extended support brackets 38 and 39 which are rollably supported on the transverse horizontal support shafts 42 and 43 preferably by means of the anti-friction bearing means 40 and 41, respectively. As shown in FIG. 2, the other threading rail 37 is similarly provided with the support brackets 44 and 45 which are mounted by means of the anti-friction means 46 and 47 on the support shafts 48 and 49, respectively.

As shown in FIG. 4, the outer end of the support shaft 42 is suitably supported in the journal member 52 carried by the support roll frame plate 17. The outer end of the support shaft 48 is suitably journalled in the journal member 51 carried by the support roll frame plate 16. The inner ends of the support shafts 42 and 43 are operatively mounted in the journal member 50 carried by the intermediate support roll frame plate 18. The support shaft 43 is supported at its outer end by the journal member 55 carried by the frame plate 16 of the first support roll assembly and the inner end thereof is operatively mounted in the journal 53 carried by the frame plate 18. The support shaft 49 has its inner end operatively mounted in the journal member 53 and its outer end in the journal member 54 carried in the frame plate 17 of the first support roll assembly.

The threading rails 36 and 37 are adapted to be moved toward and away from each other by means of the power cylinder shown in FIGS. 2 and 3 and generally indicated by the numeral 56. The power cylinder 56 may be of any suitable type fluid motor as, for example, a pneumatically operated or hydraulic fluid operated cylinder. As best seen in FIG. 3, the fluid cylinder 56 is horizontally disposed and has one end thereof integrally connected by means of the pin 57 to the bracket 58 which is fixed, as by welding, to the frame plate 17 of the first support roll assembly. As shown in FIG. 3, the fluid cylinder 56 is provided with the cylinder rod 59 which extends outwardly and transversely through the hole 62 in the frame plate 18. Mounted on the outer end of the cylinder rod 59 is the yoke 60 which is hingedly connected by means of the pin 61 to the threading rail 36. It will be seen that when the fluid cylinder 56 is operated in the conventional manner to make the cylinder rod 59 move inwardly and outwardly, the threading rail 36 will be moved laterally across the length of the support shafts 42 and 43, as shown in FIGS. 2 and 4. V

The threading rail 37 is interconnected with the threading rail 36 by the following described structure so that the threading rail 37 will move relative to the threading rail 36 in a predetermined manner. As shown in FIG. 4, a first elongated, longitudinally extended chain sprocket shaft is formed along the outer side of the threading rail 37, and it comprises the pair of aligned shafts 63 and 64 which are connected at their inner ends by the coupling member 65. The outer ends of the shafts 63 and 64 are suitably journalled in the journal members 66 and 67, respectively, which are suitably fixed on the adjacent frame plates of the first and second support roll assemblies. A similar second chain sprocket shaft is provided along the outer side of the other threading rail 36, as shown in FIGS. 1 and 4. This second chain sprocket shaft comprises the axially disposed shafts 68 and 69 which are suitably secured together at the inner ends thereof by the coupling 70. The outer ends of the shafts 68 and 69 are suitably journalled in the journal members 71 and 72 which are suitably secured to the outer frame plates of the first and second support roll assemblies. It will be understood that the first and second chain sprocket shafts are horizontally disposed on the same plane and are rotatably mounted in their aforedescribed supporting journals.

As shown in FIGS. 2 and 4, a chain sprocket 73 is fixedly mounted on the shaft 68 adjacent the shaft journal 71. A similar chain sprocket 74 is fixedly mounted on the shaft 63 in transverse alignment with the sprocket 73. A continuous suitable drive chain is threaded around the sprockets 73 and 74. As shown in FIG. 2, a suitable chain gripper 77 is carried by the support bracket and is operatively connected to the upper pass 75 of the continuous chain. The supporting bracket 39 is similarly connected by means of the chain gripper 78 to the lower pass 76 of the continuous chain. As shown in FIG. 4, a similar chain and sprocket structure interconnects the support brackets 38 and 44 and the corresponding parts have been marked with similar reference numerals followed by the small letter a. It will be seen that when the fluid cylinder 56 is operated to move the threading rail 36 laterally inwardly and outwardly, the threading rail 37 will be moved in a similar manner. That is, as the I threading rail 36 is moved inwardly, the threading rail 37 will also be moved inwardly and so forth.

The operation of the threading rail apparatus of the present invention will be described relative to FIGS. 1 and 4. When a new supply coil of strip stock is mounted on the strip stock processing apparatus in which the threading rail apparatus of the present invention is incorporated, the rails 36 and 37 are moved laterally toward each other so as to support the leading edge of the strip stock as it is fed from the stock straightener machine 11 toward the stock-length feeding machine 12. The leading edge of the new coil of strip stock will emerge from the straightener machine 11 onto the support rolls 15 and will thence move to the left, as shown in FIG. 1, until it engages the rails 36 and 37. The leading edge of the strip stock then moves to the left, as shown in FIG. 1, across the length of the rails 36 and 37 onto the support rolls 14 adjacent the stock-length feeding machine 12. The machine 12 is adapted to secure the leading edge of the new strip between suitable drive rolls, and the rails 36 and 37 then move laterally outward to allow the strip stock to form a catenary loop between the rails, as indicated by the broken line in FIG.

1. The rails 36 and 37 then continue to exert lateral guide threading rails of the present invention is that they can be set so as to feed the strip stock material 13 in an off center position. In order to make this off center ad justment, the chain grippers 77 and 78 may be adjusted relative to each other to provide a required off center positioning of the threading rails 36 and 37 relative to each other. The chain and sprocket drive arrangement provides an accurate and positive adjustment means for the threading rails 36 and 37 and maintains these rails in a parallel disposition.

FIGS. 5 through 8 illustrate a second embodiment of the invention wherein the threading rails are adapted to carry some of the support rolls at the stock-length feed machine end directly on the ends of the threading rails. As shown in FIGS. 6 and 6A, the support roll frame structure for the second embodiment is the same as employed in the first embodiment of FIG. 1, and the corresponding frame plates have been provided with the same reference numerals. The support roll frame plates 16, 17 and 18 in this second embodiment are interconnected at the lower ends thereof with the same type of tie rods 28 and 31 as were employed in the first embodiment and in addition thereto they are provided with an upper set of these tie rods which have been marked with the same reference numerals followed by the small letter a (FIG. 6). As shown in FIGS. 6 and 6A, the intermediate frame plate 18 is provided with a pair of stub rollers 79 and 80 which are rollably mounted on the shaft 81 that is journalled in the hub member 82. The hub member 82 is integrally formed with the frame plate 18. The stub rollers 79 and 80 are secured on the outer ends of the shaft 81 by any suitable means, as by the conventional clip rings 83. As shown in FIG. 6A, the frame plate 18 carries two other sets of stub rollers, and they have been marked with the same reference numerals followed by the letters a and b. As shown in FIG. 6, the threading rail 37a is provided at the outer end thereof with the journal member 84 in which is suitably journalled the roll shaft 85. A stub roll 86 is rotatably mounted by suitable bearings, as 87, on the inner end of the shaft 85. As shown in FIG. 6, the threading rail 36a is also provided with the journal member 88 which operatively carries the roll shaft 89. Rotatably mounted on the inner end of the shaft 89, by means of the bearings 90, is the support roll 91 which is identical to the roll 86. As shown in FIGS. 6 and 6A, the threading rails 36a and 37a have been provided with additional stub support rolls and they have been marked with similar reference numerals followed by the small letters b and 0.

An advantage of having the support stub rolls mounted directly on the threading rails is that there is less inertia to contend with during a feeding operation and less chance of scoring the surface of the strip stock material 13 as it is fed into the stock-length feed machine 12. The strip stock material is subject to such scoring or marring of the surface because of the different speeds of the feeding machine 12. The feeding machine 12 runs in a cyclic manner, that is, it speeds up and slows down. Accordingly, once the threading rails have been set in position, it is necessary to retain them in position by means of a brake means shown in FIGS. 7 and 8. The brake is generally indicated by the numeral 92 and is provided with a brake drum having a hub 93 which is fixedly mounted by any suitable means on the one end of the chain sprocket shaft 69. The flange 94 of the brake drum is adapted to be operatively engaged by the brake shoes 95 and 96 for holding the shaft 69 in place whereby the threading rails will not move from a set position. The brake shoes 95 and 96 are operatively connected by means of the pivot pins 98 and 99 to the brake operating lever 97. One end of the brake shoe 96 is anchored, by means of the anchor pin 100, to the bracket 101 mounted on the support roll frame plate 17. The brake operating lever 97 is hingedly connected by means of the pin 102 to the cylinder rod 103 of the fluid cylinder 104. The cylinder 104 may be any suitable fluid cylinder as, for example, a pneumatic cylinder or a hydraulic fluid cylinder. It will be seen that when the fluid cylinder 104 is operated so as to move the cylinder rod 103 downwardly as viewed in FIG. 8, the brake shoes and 96 will grip the brake drum flange 94 to prevent the shaft 69 from rotating and will function to retain the threading rails in the desired set position. When the fluid cylinder 104 is operated in the reverse direction, the shaft 69 will be free to rotate to set the threading rails in a new adjusted position.

While it will be apparent that the preferred embodiments of the invention herein disclosed are well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

What we claim is:

1. In a strip stock processing assembly, the combination comprising: a strip stock threading rail apparatus including a pair of elongated rails, drive means interconnecting said elongated rails for moving the rails toward and away from each other to selected adjusted positions when one of said rails is moved; power means connected to at least one of said rails for moving the same; said drive means interconnecting said elongated rails and comprising a pair of idler shafts disposed on opposite sides of the elongated rails, a chain and sprocket means interconnecting each of the adjacent ends of said shafts, and each of said chain and sprocket means being operatively connected to said elongated rails whereby when one rail is moved the other rail will be correspondingly moved.

2. The strip stock feeding machine as defined in claim 1, wherein: said power means comprises a fluid cylinder connected to a first one of said rails for moving the same, whereby the second rail is correspondingly moved by said interconnecting drive means.

3. In a strip stock processing assembly, the combination comprising: a first strip stock support means adapted to be connected to a first strip stock processing machine in said assembly; a second strip stock support means adapted to be connected to a second strip stock processing machine in said assembly; a strip stock threading rail apparatus operatively connected between said first and second strip stock support means for supporting and guiding the leading edge of a strip of stock from the first support means to the second support means, and for lateral guiding of the strip stock between said procesing machines after said leading edge has entered the second strip stock processing machine; and, said first and second strip stock support means each comprising a plurality of support rolls.

4. In a strip stock processing assembly, the combination comprising: a first strip stock support means adapted to be connected to a first strip stock processing machine in said assembly; a second strip stock support means adapted to be connected to a second strip stock processing machine in said assembly; a strip stock threading rail apparatus operatively connected between said first and second strip stock support means for supporting and guiding the leading edge of a strip of stock from the first support means to the second support means, and for lateral guiding of the strip stock between said processing machines after said leading edge has entered the second strip stock processing machine; and, said first and second strip stock support means each comprising a plurality of support rolls including at least one support roll made from a resilient material.

5. In a strip stock processing assembly, the combination comprising: a first strip stock support means adapted to be connected to a first strip stock processing machine in said assembly; a second strip stock support means adapted to be connected to a second strip stock processing machine in said assembly; a strip stock threading rail apparatus operatively connected between said first and second strip stock support means for supporting and guiding the leading edge of a strip of stock from the first support means to the second support means, and for lateral guiding of the strip stock between said processing machines after said leading edge has entered the second strip stock processing machine; said threading rail apparatus being provided with a plurality of support rollers adapted to coact with said second support means; and, said first and second strip stock support means each comprising a plurality of support rolls.

6. In a strip stock processing assembly, the combination comprising: a first strip stock support means adapted to be connected to a first strip stock processing machine in said assembly; a second strip stock support means adapted to be connected to a second strip stock processing machine in said assembly; a strip stock threading rail apparatus operatively connected between said first and secsecond strip stock support means for supporting and guiding the leading edge of a strip of stock from the first support means to the second support means, and for lateral guiding of the strip stock between said processing machines after said leading edge has entered the second strip stock processing machine; said threading rail apparatus being provided with a plurality of support rollers adapted to coact with said second support means; and, said first and second strip stock support means each comprising a plurality of support rolls including at least one support roll made from a resilient material.

7. In a strip stock processing assembly, the combination comprising: a first strip stock support means adapted to be connected to a first strip stock processing machine in said assembly; a second strip stock support means adapted to be connected to a second strip stock processing machine in said assembly; a strip stock threading rail apparatus operatively connected between said first and second strip stock support means for supporting and guiding the leading edge of a strip of stock from the first support means to the second support means, and for lateral guiding of the strip stock between said processing machines after said leading edge has entered the second strip stock processing machine; said threading rail apparatus being provided with a plurality of support rollers adapted to coact with said second support means; said first and second strip stock support means each comprising a plurality of support rolls; and, a brake means connected to said threading rail apparatus and operative to hold the threading rail apparatus in selected adjusted positions.

8. The strip stock processing assembly as defined in claim 7, wherein: said plurality of support rolls includes at least one support roll having a resilient covering.

9. In a strip stock processing assembly, the combination comprising: a first strip stock support means adapted to be connected to a first strip stock processing machine in said assembly; a second strip stock support means adapted to be connected to a second strip stock processing machine in said assembly; a strip stock threading rail apparatus operatively connected between said first and second strip stock support means for guiding strip stock between said processing machines; said strip stock threading rail apparatus including a pair of elongated rails, drive means interconnecting said elongated rails for moving the rails toward and away from each other to selected adjusted positions when one of said rails is moved; power means connected to at least one of said rails for moving the same; and, said drive means interconnects said elongated rails and comprises a pair of idler shafts disposed on opposite sides of the elongated rails, a chain and sprocket means interconnecting each of the adjacent ends of said shafts; and, each of said chain and sprocket means being operatively connected to said elongated rails, whereby when one rail is moved the other rail will be moved correspondingly.

10. In a strip stock processing assembly, the combination comprising: a first strip stock support means adapted to be connected to a first strip stock processing machine in said assembly; a second strip stock support means adapted to be connected to a second strip stock processing machine in said assembly; a strip stock threading rail apparatus operatively connected between said first and second strip stock support means for guiding strip stock between said processing machines; said strip stock threading rail apparatus including a pair of elongated rails, drive means interconnecting said elongated rails for moving the rails toward and away from each other to selected adjusted positions when one of said rails is moved; power means connected to at least one of said rails for moving the same; and, said power means comprising a fluid cylinder connected to a first one of said rails for moving the same, whereby the second rail is moved correspondingly by said interconnecting drive means.

References Cited UNITED STATES PATENTS 635,792 10/1899 Mansfield 271-59X 2,072,122 3/1937 Montgomery.

2,277,514 3/1942 Elser 226-108 2,308,591 1/1943 Duffy etal. 198-204 2,365,322 12/1944 Ashworth 226179 2,706,034 4/1955 Russell et al 198204 2,726,859 12/1955 Dolanore 226189 2,883,244 4/1959 Berger 308-6 3,177,749 4/1965 Best et al. 226 118 M. HENSON WOOD, JR., Primary Examiner.

S. H. SPADERNA, I. N. ERLICH, Assistant Examiners. 

1. IN A STRIP STOCK PROCESSING ASSEMBLY, THE COMBINATION COMPRISING: A STRIP STOCK THREADING RAIL APPARATUS INCLUDING A PAIR OF ELONGATED RAILS, DRIVE MEANS INTERCONNECTING SAID ELONGATED RAILS FOR MOVING THE RAILS TOWARD AND AWAY FROM EACH OTHER TO SELECTED ADJUSTED POSITIONS WHEN ONE OF SAID RAILS IS MOVED; POWER MEANS CONNECTED TO AT LEAST ONE OF SAID RAILS FOR MOVING THE SAME; SAID DRIVE MEANS INTERCONNECTING SAID ELONGATED RAILS AND COMPRISING A PAIR OF IDLER SHAFTS DISPOSED ON OPPOSITE SIDES OF THE ELONGATED RAILS, A CHAIN AND SPROCKET MEANS INTERCONNECTING EACH OF THE ADJACENT ENDS OF SAID SHAFTS, AND EACH OF SAID CHAIN AND SPROCKET MEANS BEING OPERATIVELY CONNECTED TO SAID ELONGATED RAILS WHEREBY WHEN ONE RAIL IS MOVED THE OTHER RAIL WILL BE CORRESPONDINGLY MOVED. 